Over the last decade, the research work of many pharmaceutical and biotechnology companies has focused on the generation of biological products using recombinant DNA technology. Such biopharmaceutical products include e.g. enzymes, synthetic hormones, vaccines, monoclonal antibodies, cytokines. Whilst simple proteins can be produced using bacterial cultures, more complex proteins with a requirement for carbohydrate modification, e.g. glycosylation, assembly of different subunits, correct folding and functionality need to be produced in mammalian cells. Mammalian cell cultures are traditionally used for the production of glycosylated recombinant protein products and commonly used cell lines include, Chinese hamster ovary (CHO) cells, 293 Human embryonic Kidney (HEK) cells, COS cells, Baby Hamster Kidney (BHK) cells, PER.C6® and mouse myeloma cell lines such as NS0 or Sp2/0.
Since recombinant proteins for the therapy of human diseases need to have natural folding and post-translational modification and because they need to remain pharmacologically active for a defined shelf-life, supply of recombinant proteins for clinical studies and therapy requires the development of a highly reproducible and controlled production process. Such a process should ensure high quality and stability of the product in accordance with the quality obligations of the regulatory authorities at an acceptable cost of goods.
Mammalian cell lines, which allow the production of therapeutic proteins, are required to have high productivities and stable phenotypic and genotypic product expression profiles. The introduction of genetic information into a host cell genome by the process of DNA transfection is acknowledged to be an inefficient process. Therefore the present invention addresses this problem by utilising a method of retroviral transduction to achieve highly efficient transfer of genetic information into the genome of host cells. A current method of retroviral expression of recombinant proteins in the only industry approved production cell line utilises a pantropic vector with the ability to infect all species and therefore requires a Bio safety level 2 (BSL2) system (Bleck, 2005). This is a potential safety concern for the generation of therapeutic proteins resulting in higher costs during production to ensure staff safety and comply with the associated regulations. These drawbacks can be overcome by the use of an ecotropic retrovirus vector particle as described in the present invention, which has a restricted host cell infectivity and can therefore be used without safety concerns, resulting in lower production costs.